Metallized particle interconnect with solder components

ABSTRACT

An electrical connection is established between a first electrical component and a second electrical component of an assembly and a compression tool is used to apply a compression force to the assembly. The assembly also includes a metallized particle interconnect (MPI) between the first electrical component and the second electrical component and solder components outside a boundary of the MPI and extending from the first electrical component to the second electrical component. The solder components are melted by applying heat to the assembly. The solder components are solidified by cooling the assembly and the compression tool is removed.

BACKGROUND

The present disclosure relates to connecting electrical components, andmore specifically, to connecting electrical components using ametallized particle interconnect (MPI) and solder components.

Electrical components can be stacked using interconnect technology.Interconnect technology can include the use of solder reflow to makeelectrical connections, the use of wiping contacts to make electricalconnections, the use of filled adhesives to make electrical connections,and the use of sheet materials such as MPIs to make electricalconnections. Each of these technologies has its advantages and can havedifferent methods of establishing the connections. Printed circuitboards (PCBs) are used in many electronic products. As technology hasadvanced, electrical devices have become more compact and at the sametime, the number of electrical components on a PCB continues toincrease. As a result, the amount of space on a PCB has become an issueand electrical component stacking using interconnect technology is oneway to address this issue.

SUMMARY

According to embodiments of the present disclosure, a method isdisclosed for connecting electrical components. In various embodimentsthe method may include establishing an electrical connection between afirst electrical component and a second electrical component using acompression tool to apply a compression force to an assembly. In certainembodiments the assembly may include the first electrical component, thesecond electrical component, a metallized particle interconnect (MPI)between the first electrical component and the second electricalcomponent, and a set of solder components outside a boundary of the MPIand extending from the first electrical component to the secondelectrical component. The method may also include melting the set ofsolder components by applying heat to the assembly. In addition, themethod may include solidifying the set of solder components by coolingthe assembly. Furthermore, the method may include removing thecompression tool.

According to embodiments of the present disclosure, a device isdisclosed. In various embodiments, the device may include a firstelectrical component having a top surface and a bottom surface andhaving an electrical contact. The device may also include a secondelectrical component having a top surface and a bottom surface andhaving an electrical contact. In addition, the device may include ametallized particle interconnect (MPI) under compression between thefirst electrical component and the second electrical component having atop surface and a bottom surface and having conductive columns thatextend from the top surface of the MPI to the bottom surface of the MPI.Furthermore, the device may include a set of solder components outside aboundary of the MPI and extending from the bottom surface of the firstelectrical component to the top surface of the second electricalcomponent. The solder components may also be configured to maintain thecompression of the MPI between the first electrical component and thesecond electrical component.

According to embodiments of the present disclosure, a kit is disclosed.In various embodiments, the kit may include a first electrical componentconfigured to receive a compression force, having a solder padconfigured to maintain compression and having an electrical contact. Thekit may also include a second electrical component configured to receivethe compression force, having a solder pad configured to maintaincompression and having an electrical contact. Furthermore, the kit mayinclude a metallized particle interconnect (MPI) configured to receivethe compression force between the first electrical component and thesecond electrical component, having conductive columns that extend froma top surface of the MPI to a bottom surface of the MPI. The MPI mayalso be configured to electrically connect the electrical contact of thefirst electrical component and the electrical contact of the secondelectrical component.

The above summary is not intended to describe each illustratedembodiment or every implementation of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in the present application are incorporated into,and form part of, the specification. They illustrate embodiments of thepresent disclosure and, along with the description, serve to explain theprinciples of the disclosure. The drawings are only illustrative ofcertain embodiments and do not limit the disclosure.

FIG. 1 depicts a PCB electrically connected to electrical components,consistent with embodiments of the present disclosure;

FIG. 2 depicts two electrical components electrically connected,consistent with embodiments of the present disclosure;

FIG. 3 depicts multi-stack electrical components electrically connected,consistent with embodiments of the present disclosure;

FIG. 4 depicts a kit for electrically connecting electrical components,consistent with embodiments of the present disclosure; and

FIG. 5 depicts a method for connecting electrical components, consistentwith embodiments of the present disclosure.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to connecting electricalcomponents, more particular aspects relate to connecting electricalcomponents using a metallized particle interconnect (MPI) and soldercomponents. While the present disclosure is not necessarily limited tosuch applications, various aspects of the disclosure may be appreciatedthrough a discussion of various examples using this context.

Various embodiments of the present disclosure are directed toward ametallized particle interconnect (MPI) that electrically connectselectrical components and is kept under compression between theelectrical components using solder bonds. Accordingly, particularembodiments can use particle enhanced joining technology to provideelectrical connections between the many various electrical components,subassemblies, and assemblies that can include, but are not limited to,integrated chips (ICs), printed circuit boards (PCBs), flexibleelectronics (e.g., backplanes), and electronic optical modules (e.g.,detectors, transmitters, and sensors). Furthermore, in certainembodiments, the electrical components can have electrical contactsconfigured to allow current to flow to and from the electricalcomponent. Metals used as electrical contacts can include, but are notlimited to, aluminum, platinum, titanium, tungsten, chrome, nickel,gold, silicon, iron, copper, cobalt, silver, molybdenum, lead, tin,indium, and various alloys.

In various embodiments, a compression tool can be used to apply pressureto the electrical components and MPI. Solder reflow technology can thenbe used to create a bond between the electrical components. When thesolder has cooled and the bond has formed, the compression tool can beremoved and the solder bond can hold the electrical components in place.This can maintain the compression of the MPI between the electricalcomponents in the absence of a compression tool and allow the MPI tomaintain the electrical connection of the electrical components.

As discussed herein, an MPI can allow two or more electrical componentsto be electrically connected as an alternative to using solderconnections, which require the application of heat. Instead of usingheat to create electrical connections, electrical connections using MPIscan be created when the electrical components, having electricalcontacts, are brought together under pressure. MPIs can be configuredwith conductive columns that are designed in a pattern to match thepattern of the electrical contacts. The conductive columns can beconstructed from conductive particles embedded in the MPI and when theMPI is pressed against the electrical components (e.g., by using acompression tool) the conductive columns can impinge upon the electricalcontacts, allowing an electrical connection to be established from oneelectrical component to another.

Various embodiments are directed towards electrical components and MPIsthat are configured into many geometric shapes including flat, curved,and irregular. In particular embodiments, the electrical components andMPIs will have shapes that substantially mirror one another such thatthe two surfaces to be bonded may be brought together along a commoninterface. In other embodiments, the two surfaces may not mirror oneanother and it may be necessary to adjust the mating surfaces so theyfit together.

Interconnect technology uses several methods for interconnectingelectronic components. For instance, solder components (e.g., solderballs) can be used to electrically connect electrical components fordigital applications. However, solder components can present ahigh-inductance path that could exceed 1 nH. While suitable for lowerspeed, digital links, the high-inductance path of a solder componentpossesses challenges for higher speed digital links, radio frequency(RF) applications, and high-transient current operations. MPIs can beused as an alternative electrical component connection that can have acomparatively low-inductance interconnect that, in particularembodiments, can reach below 0.3 nH. This can work well with high-speeddigital links, RF applications, and high-transient current operations.However, an electrical component (e.g., PCBs) may not have the space forcompression tools. These compression tools may be necessary to apply thecompression for the MPI to work properly during the operation of theelectrical component. Accordingly, in certain embodiments, when anelectrical connection has been established, solder pads and soldercomponents (e.g., solder balls) can be arranged outside a boundary ofthe MPI and reflow technology can be used to maintain the compressionfor the MPI to work properly.

Various embodiments are directed toward electrically connectingelectrical components using surface-mount technology (SMT). SMT is amethod for producing electrical circuits in which an electricalcomponent is mounted or placed directly onto the surface of anotherelectrical component. In particular embodiments, to mount electricalcomponents, reflow soldering can be used. Reflow soldering is a processin which solder pads can be arranged and solder paste can be placed onthe pads, heated, and then cooled to attach the electrical components.During reflow, a stencil can be used. The stencil can have apertures anda solder paste can be printed through a stencil aperture to form a bondthat holds an electrical component in place and, when reflowed, securesit to another electrical component. As a result, the stencil aperturescan determine the size, shape, and positioning of the solder components.For the electrical components to stay electrically connected, a reliablebond may be necessary to meet compression requirements of the MPI. Thesize, shape, and positioning of the solder components can all affect thereliability of the bond.

In various embodiments, the area and the shape of the MPI can affect thesize, shape, and positioning of the solder components. In addition,multiple reflow processes can affect the strength of the soldercomponents. To generate solder components with the size, shape,positioning, and strength that satisfy the MPI compression requirements,the stencil printing process may need to be considered. There can bemany variables that influence the quality of the stencil printingprocess, which is measured by the amount and position of the soldercomponents deposited. These variables can include, but are not limitedto, stencil thickness, solder component type, electrical componentfinish, printing process speed, stencil aperture size, and stencilaperture shape. For example, the size and shape of the stencil aperturecan determine the volume, uniformity and definition of a soldercomponent. During the printing process, the ability of the soldercomponent to release from the stencil can depend on an area ratio and anaspect ratio of the stencil. The area ratio can be defined as the ratioof the area of the stencil aperture to the area of a sidewall of thestencil aperture. The aspect ratio can be defined as the width of theinside wall of the stencil aperture divided by the thickness of thestencil. For mounting an electrical component to another electricalcomponent, an area ratio greater than 0.66 and an aspect ratio greaterthan 1.5 can be acceptable. However, because various embodiments aredirected toward solder components that are satisfying compressionrequirements of an MPI and may be subject to multiple reflow processes,in particular embodiments, the area ratio and aspect ratio may be largerthan prior ratios.

Consistent with various embodiments, the size and configuration of thesolder pads can be designed according to the bond failure strength ofthe particular solder being used and according to the pressurerequirements of the MPI connector. For example, solder of type Sn3.5Aghaving a solder diameter size of 0.76 mm, a solder pad size of 0.64 mm,and a solder pitch of 1.27 mm may experience bond failure at a pullstrength of around 2800 grams after one reflow. An MPI connector mayrequire 10 to 12 grams of contact pressure per electrical contact. Thenumber and/or size of the pads can therefore be set as a function of thesize of the MPI connector. Moreover, the pads can be designed for soldertypes having different melting points. For example, Sn3.5Ag may have amelting point of 221 degrees Celsius and a solder of type SAC can have amelting point of 217 degrees Celsius. Furthermore, SAC having a solderdiameter size of 0.76 mm, a solder pad size of 0.64 mm, and a solderpitch of 1.27 mm may experience bond failure at a pull strength ofaround 2600 grams after one reflow. Thus, the pads can be designed forthe worst case solder bond strength (e.g., SAC having a bond failurerate at a pull strength of around 2400 grams after six reflows) or adifferent pad design can be used for each level of a stacked device.

Particular embodiments are directed toward solder bonds that aredesigned to maintain the pressure first applied by a compression tool inorder to establish the electrical connection before the reflow process.After reflow, the compression tool can then be removed, leaving thesolder bond to counteract the repulsive force of the MPI on theelectrical components. As a result, the MPI can maintain theinterconnection of the electrical components, taking advantage of itslow-inductance properties, and provide a solution for space criticalapplications, such as mobile devices.

In addition, because the solder bond maintains the compression on theMPI, a compression tool (e.g., a bolster plate and screws) thatsurrounds the electrical component may no longer be required, or mayhave reduced load requirements. In certain embodiments, this leads toextra space on the PCB. This space can be used for a variety of purposesthat can include, but are not limited to, additional circuit componentsor a heat sink that is designed to cool the electrical component and mayallow the electrical component to function more efficiently and for alonger period of time.

Furthermore, when dealing with electrical components, electromagneticinterference (EMI) is often a consideration. EMI are disturbance singlesthat interrupt, obstruct, degrade, or limit the effective performance ofelectrical components and electrical equipment. There may be instanceswhere low frequency interference may be present. Therefore, inparticular embodiments, where the solder bonds also establish anelectrical connection between the electrical components, a groundingconnection that decouples low frequency signals can be obtained,decreasing EMI emissions. For example, the ground or power from the PCBcan be routed between the electrical components using the solderconnections. In certain embodiments, data signals could also be routedusing the solder connections.

Turning now to the figures, FIG. 1 depicts a PCB 100 electricallyconnected to electrical components, consistent with embodiments of thepresent disclosure. A PCB can include electrical components such as ICs(e.g., single stack ICs 102, 104, 106, double stack ICs 108, 110, andtriple stack ICs 112, 114), microprocessors 116 and 118, memory modules(e.g., dual in line memory modules (DIMMs) and single in line memorymodules (SIMMs)) 120-134 and 136-150, and passive electrical elements(e.g., resistors and capacitors) and wirings (not shown in FIG. 1) usedto connect these electrical components. The electrical components can beconnected to the PCB 100 using SMT. One method to mount electricalcomponents to a PCB is using ball grid array (BGA) packaging. In certainembodiments, BGA packages can be used to mount microprocessors 116 and118 to the PCB 100.

Consistent with embodiments, the single stack ICs 102, 104, 106, thedouble stack ICs 108, 110, and the triple stack ICs 112, 114 can beelectrically connected to the PCB 100 (and to other ICs in the stack)using one or more MPIs (e.g., MPIs 154). For example, an electricalconnection can be created by placing an MPI 154 between the double stackIC 108 and the PCB 100. MPI 154 can be configured with conductivecolumns (not shown in FIG. 1) designed in a pattern to match the patternof the electrical contacts (not shown in FIG. 1) on the double stack IC108 and the PCB 100. The double stack IC 108 and the PCB 100 can then bebrought together under pressure using a compression tool (e.g., clampsand brackets). As a result, the MPI can press against the double stackIC and the PCB and the conductive columns can impinge upon theelectrical contacts, allowing an electrical connection to be establishedbetween the double stack IC and the PCB.

The double stack IC 108 can then be mounted to the PCB 100 using reflowtechnology. For instance, solder pads (not shown in FIG. 1) can bearranged around the MPI 154 and solder components 152 can be placed onthe pads to attach the double stack IC to the PCB. While the doublestack IC and the PCB are compressed by a compression tool, heat can beapplied to melt the solder components 152. Heating may be accomplishedusing several methods, including but not limited to, passing the PCBthrough a reflow oven, placing the PCB under an infrared lamp, or bymelting individual solder components with a hot air pencil. The soldercomponents can then be cooled, forming a bond that affixes the doublestack IC to the PCB. The compression tool can then be removed, leavingthe solder components to counteract the repulsive force of the MPI onthe double stack IC and the PCB. As a result, the MPI can maintain theelectrical connection between the double stack IC and the PCB.

The example above was described with respect to the double stack IC 108and PCB 100. However, the example can also describe the single stack ICs102, 104, and 106 or the triple stack ICs 112 and 114 being electricallyconnected and mounted to the PCB 100. Furthermore, a similar process canbe used to assemble the double stack ICs 108, 110 and the triple stackICs 112, 114 or multi-stack electrical components in general. Forinstance, the MPIs 154 can electrically connect a top and bottomelectrical component comprising the double stack ICs 108 and 110 and thesolder components 152 can mount the top electrical component to thebottom electrical component. The double stack ICs 108 and 110 can thenbe electrically connected and mounted to the PCB 100. In anotherembodiment, a single stack electrical component can be electricallyconnected to the PCB 100 and then multiple electrical components can bestacked on top, creating a multi-stack electrical component. In eitherembodiment multiple reflow steps can be used to place each IC and toform and fix each corresponding MPI connection. For example, highertemperature solder components can be used for the initial mounting andlower temperature solder components can be used for later mounting. Thiscan ensure that the previously connected and mounted electricalcomponents do not separate during the succeeding reflow processes.

FIG. 2 depicts two electrical components electrically connected,consistent with embodiments of the present disclosure. A top electricalcomponent 202 (e.g., an IC, a PCB, and a package (interface between anIC and a PCB)) can be electrically connected to a bottom electricalcomponent 204 (e.g., an IC or PCB). Both electrical components 202 and204 can be configured with electrical contacts 208. The electricalcomponents 202 and 204 can be electrically connected using the MPI 154,configured with conductive columns 206, similar to the way the doublestack IC was electrically connected to the PCB 100, described in FIG. 1.Furthermore, the top electrical component 202 can be mounted to thebottom electrical component 204 using solder pads 210 and soldercomponents 154 similar to the way the double stack IC was mounted to thePCB 100, described in FIG. 1.

The double headed arrows shown in MPI 154 represent the repulsive forcethat the MPI displaces upon the top electrical component 202 and thebottom electrical component 204. The arrows shown in solder components152 represent the compressive force that the solder components displaceupon the top electrical component 202 and the bottom electricalcomponent 204 to counteract the repulsive force. The solder components154 may contain many different metals including, but not limited to,tin, copper, silver, bismuth, indium, zinc, and antimony. The soldercomponents apply the compressive force that can replace the compressiveforce applied by a compression tool that is used to initiallyelectrically connect the top electrical component 202 to the bottomelectrical component 204. The compression tool can apply a force that isnecessary for the electrical contacts 208 to make contact with theconductive columns 206. When the solder components 152 have cooled andthe top electrical component 202 is mounted to the bottom electricalcomponent 204, the compression tool can be removed. The soldercomponents 152 can then continue to apply the compression force thatkeeps the electrical contacts 208 from being removed from the upperlayer of the conductive columns 206.

FIG. 3 depicts multi-stack electrical components electrically connected,consistent with embodiments of the present disclosure. Similar to FIG.2, the double headed arrows in MPI 154 represent the repulsive force andthe arrows shown in solder components 308 and 310 represent thecompressive force counteracting the repulsive force. In certainembodiments where multiple reflows occur, it can be preferred to usesolder components that have higher melting points in earlier reflows andsolder components with lower melting points in later reflows. This cansimplify the multi-stacking process. For instance, if solder componentswith higher melting points are used in earlier reflows, only onecompression tool may need to be used multiple times to establish theinitial electrical connection between the electrical components.However, if solder components with lower melting points are used in anearlier reflow, multiple compression tools may be needed to applydifferent amounts of compression to multiple electrical components tokeep the electrical components from shifting and maintain electricalconnections where the solder components have melted. For example, a topelectrical component 302 can first be electrically connected to a middleelectrical component 304 and then mounted to the middle electricalcomponent using solder pads 210 and solder components 308. Then themiddle electrical component 304 can be electrically connected to thebottom electrical component 306 and then mounted to the bottomelectrical component using solder pads 210 and solder components 310. Inthis embodiment, the solder components 308 will be made of a materialthat has a higher melting point than solder components 310 so that whenthe reflow process is done again to mount the middle electricalcomponent to the bottom electrical component, the solder components 308will not melt.

In another embodiment, the middle electrical component 304 can first beelectrically connected to the bottom electrical component 306 and thenmounted to the bottom electrical component using solder pads 210 andsolder components 310. Then the top electrical component 302 can beelectrically connected to the middle electrical component 304 and thenmounted to the middle electrical component 304 using solder pads 210 andsolder components 308. In this embodiment, the solder components 310will be made of a material that has a higher melting point than soldercomponents 308 so that when the reflow process is done again to mountthe top electrical component to the middle electrical component, thesolder components 310 will not melt.

FIG. 4 depicts a kit 400 for electrically connecting electricalcomponents, consistent with embodiments of the present disclosure. Thekit 400 can include electrical components 402 configured with electricalcontacts 410 and solder pads 408, an MPI 404 configured with conductivecolumns 412, and a compression tool 414. The electrical components 402can be electrically connected using the MPI 404 and the compression tool414, similar to the way the double stack IC 108 is electricallyconnected to the PCB 100, described in FIG. 1. The double headed arrowsshown near the compression tool 414 illustrate the adjustability of thecompression tool so that different amounts of pressure can be applied tothe electrical components 402. Furthermore, the electrical components402 can be mounted to one another using the solder pads 408, similar tothe way the double stack IC 108 is mounted to the PCB 100, described inFIG. 1.

FIG. 5 depicts a method 500 for connecting electrical components,consistent with embodiments of the present disclosure. In operation 502,an electrical connection is established between a first electricalcomponent and a second electrical component. The first electricalcomponent and the second electrical component can both be configuredwith electrical contacts. The electrical connection can be establishedby placing an MPI between the first electrical contact and the secondelectrical contact. The MPI can be configured with conductive columnsthat are designed in a pattern to match the pattern of the electricalcontacts. The MPI can then be compressed between the first electricalcomponent and the second electrical component using a compression tool.During compression, the conductive columns can make contact with theelectrical contacts, allowing an electrical connection to be establishedbetween the first electrical component and the second electricalcomponent.

In operation 504, solder components can be placed on solder pads outsidea boundary of the MPI. In operation 506, the solder components can bemelted through the application of heat. In operation 508, the assemblyincluding the electrical components, the MPI, the solder components, andthe solder pads, can be cooled. When the solder components havesolidified, a solder bond may have formed between the first electricalcomponent and the second electrical component. The solder bond canmaintain the pressure on the MPI that counteracts the repulsive force ofthe MPI on the first electrical component and the second electricalcomponent. As a result, the compression from the compression tool may nolonger be necessary and in operation 510, the compression tool can beremoved. In operation 512, it is determined if there are anymoreelectrical components to connect. If there are, operations 502-510 arerepeated. If there are not, method 500 is finished.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

1. A method for connecting electrical components, the method comprising:establishing an electrical connection between a first electricalcomponent and a second electrical component using a compression tool toapply a compression force to an assembly that includes: the firstelectrical component, the second electrical component, a metallizedparticle interconnect (MPI) between the first electrical component andthe second electrical component, and a set of solder components outsidea boundary of the MPI and extending from the first electrical componentto the second electrical component; melting the set of solder componentsby applying heat to the assembly; solidifying the set of soldercomponents by cooling the assembly; and removing the compression tool.2. The method of claim 1, further comprising: applying the soldercomponents to a first set of solder pads located on the first electricalcomponent.
 3. The method of claim 2, further comprising: applying thesolder components to a second set of solder pads located on the secondelectrical component.
 4. The method of claim 3, wherein the first set ofsolder pads and the second set of solder pads have sizes and aconfiguration according to a bond failure strength of the soldercomponents.
 5. The method of claim 1, wherein the solidifying of thesolder components establishes a bond between the first electricalcomponent and the second electrical component that counteracts arepulsive force of the MPI on the first electrical component and thesecond electrical component.
 6. The method of claim 1, wherein thesolidifying of the solder components establishes an electricalconnection between the first electrical component and the secondelectrical component.
 7. The method of claim 1, wherein the firstelectrical component and the second electrical component have electricalcontacts that have a common pattern.
 8. The method of claim 7, whereinthe MPI has conductive columns that extend from a top of the MPI to abottom of the MPI and match the common pattern of the electricalcontacts.
 9. The method of claim 8, wherein the electrical connection isestablished by the conductive columns making contact with the electricalcontacts when the compression force is applied. 10-19. (canceled)